SIAMESE CELL FOR GROUP-V FLUX MEASUREMENTS, UNIFORM ARSENIDE PHOSPHIDE ALLOYS, AND QUATERNARY LASERS

We have used an effusion cell with independently valved solid arsenic and red phosphorus sources and a common cracking zone to prepare extre mely uniform composition GaAs(1-x)P-x epitaxial films on 3 in. diam su bstrates. Mass spectrometry and ion gauge measurements of dimer specie s allowed determination of ionization sensitivities for phosphorus and arsenic species in good agreement with the relationship of Flaim and Ownby [J. Vac. Sci. Technol. 8, 661 (1971)]. From the mass spectromete r data, it was possible to determine the thermodynamic equilibrium con stant 1.9+/-0.4, and hence free energy -0.55 eV molecule(-1) for the p rocess As-2+P-2 double left right arrow 2 AsP. Finally double heteroju nction GaInAsP/InP lasers grown with this cell and operating at room t emperature have transparency threshold currents below 800 A cm(-2). (C ) 1996 American Vacuum Society.